It's a pivotal moment when an actor from a show you love does something as life changing as cutting his or her hair. So when we found out "Criminal Minds" star Matthew Gray Gubler made that ever-important decision to embrace the scissors, we had to find out why.

"I didn’t have to [cut it for the finale, but] I just did because I know these are always two-parters, so if you want to do something you do it before the finale. So one day I cut it and then told [the producers]," he said, joking that it was almost as scandalous as when Keri Russell cut her hair during "Felicity." "I think it was a little! I've been hearing since day one, 'Cut your hair!' and then finally I did it."

Aside from the new coif, fans will delighted to find out that the show's season finale has not skimped on the creepiness thanks to guest star, Tim Curry, who plays this week's serial killer. Not that Matthew can tell us much about what we will see.

"It's funny! I don’t really know that much about the finale. I have no idea what happens in the second part, all that I know is he's been killing for quite a while, hunting at night and he's a pretty bad guy," he said. "It's funny there's been so many bad people on the show, but he ranks up there as some of the worst."

Well, what makes him so bad? "As far as my preferences go he's up there. They're really playing him as an ultra grimy killer," he said. "He's being do this I think for decades and dedicating his life to causing misery. He made a life choice out of dismembering people."

So, who does Matthew think is the blame for all the killing? "It could have been that little rascal Kevin McAllister messing with him in 'Home Alone 2' that triggered his insanity," he joked, revealing, "I didn’t realize [Tim's] like a giant fan of 'Criminal Minds.' That’s how I think we got him. It was real shock to have someone that I admire be like, 'Hey, I love your character!' "

What do you think of MGG cutting his hair? Will you be watching tonight's "Criminal Minds" finale?